Linear actuators are employed in a variety of applications including, for example, adjustable legs for a work surface which can be moved between lowered and raised positions for use when an operator is sitting or in a standing position. Such actuators typically employ a motor mounted to the undersurface of the table and a right angle drive which extends within the telescopic table legs and couples to a drive screw for raising and lowering one of the telescopic legs with respect to the other leg utilizing a drive nut threadably coupled to the drive screw. Although such systems have found widespread use and operate to provide the desired range of motion, the utilization of a motor external to the telescopic leg is somewhat unsightly and, in many applications, esthetically unacceptable. It would be desirable, therefore, to provide a motor-driven telescopically adjustable table leg in which the drive motor can be concealed within the table leg itself.
The system of the present invention provides such an advantage by providing a drive system for an adjustable leg which includes an outer tubular leg with an inner tubular leg telescopically mounted therein. Extending from the base of the outer leg upwardly and in concentric relationship thereto is a drive nut riser tube having a drive nut mounted to an upper end thereof substantially near the upper end of the outer leg. An inner tubular leg telescopically fits within the outer leg and includes a motor mounted within the inner leg at an end remote from the outer leg. A drive screw is coupled to the motor shaft and extends through the drive nut in the drive nut riser. As the reversible motor rotates the drive screw, therefore, the inner leg extends from and retracts into the outer leg.
In a preferred embodiment of the invention, the drive nut riser is a hollow cylindrical tube extending substantially the length of the outer tube to position the drive nut near the intersection between the inner and outer legs when fully extended. Such an arrangement allows a motor to be coaxially mounted within the inner leg and, therefore, concealed to provide the desired extension and retraction of the leg for adjustment to different operative positions.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.